Solid Sample Introduction Research Articles

Direct emission spectrometry determination of fluorine in carbon materials: Argon dc arc and spark radiation sources

In this work, the procedure for direct atomic emission spectrometry (AES) determination of fluorine impurities in carbon materials was proposed. Two types of simple radiation sources with direct solid (powdered) sample introduction were studied: direct current arc (25A) and high-power low voltage spark (300 V, of 2348 μF). For each source, standard graphite extra high purity electrodes and argon discharge atmosphere were used. Red spectral region approach to non-metal AES determination was employed with analytical line F I 685.603 nm. The spectra were registered by compact tunable fiber-optic spectrometer with linear complementary metal oxide semiconductor array (CMOS) sensor and short-focus lens. Special measures were taken to counter red spectral region interferences, such as CN molecular bands and thermal radiation. The excitation of F in both types of radiation source was studied. A set of artificial graphite and NaF based standards was prepared for calibration and evaluated by two independent approaches: indirect dc arc AES and water extraction photometry. Limit of detection was determined for dc arc source was 5 μg/g, and for spark 20 μg/g of F. The whole cycle of measurement with each type of radiation source takes 10 min. As the power of dc arc is limited by generator capabilities, it is possible that even lower limit of detection is achievable with higher discharge current.

Chromatoprobe as a sample-sparing technique for residual solvent analysis of drug discovery candidates by gas chromatography

In drug discovery research, residual solvent measurement is an integral part of purity analysis for synthesis of a drug candidate before it is used for toxicity testing. This is usually carried out using gas chromatography (GC) with direct injection sample introduction. This method requires testing compounds to be soluble at high concentrations (>50mg/mL, usually in DMSO) to achieve acceptable sensitivity, a hurdle which is not always achievable for some samples such as cyclic peptides and oligonucleotides. To overcome the limitation associated with the direct injection approach, a new method using the Chromatoprobe thermal extraction device was developed for quantifying residual solvents of drug discovery compounds. This method not only consumes significantly less material (less than 1mg), but also shows higher sensitivity than the direct injection approach. In addition, because no diluent is required with the Chromatoprobe thermal extraction, all residual solvents can be detected and measured without further method optimization. In our study, we compared data from GC residual solvent analysis using the Chromatoprobe solid sample introduction to those of the direct injection method for seven in-house samples. Our results showed a good agreement between the data from these two sample introduction methods. Thus, the Chromatoprobe sample introduction method provided a sample-sparing alternative to the direct injection method for the measurement of residual solvents in drug discovery. This method can be particularly useful for residual solvent analysis in samples that are available only in limited amounts, poorly soluble, and/or unstable in the diluents used for the direct injection method.

Gas-phase detection of solid-state fission product complexes for post-detonation nuclear forensic analysis.

This study presents the first known detection of fission products commonly found in post-detonation nuclear debris samples using solid sample introduction and a uniquely coupled gas chromatography inductively-coupled plasma time-of-flight mass spectrometer. Rare earth oxides were chemically altered to incorporate a ligand that enhances the volatility of the samples. These samples were injected (as solids) into the aforementioned instrument and detected for the first time. Repeatable results indicate the validity of the methodology, and this capability, when refined, will prove to be a valuable asset for rapid post-detonation nuclear forensic analysis.

Fluorine in eye shadow: Development of method using high-resolution continuum source graphite furnace molecular absorption spectrometry via calcium mono-fluoride with direct solid sample introduction

Eye shadows are cosmetics of different colors applied in the periocular area, composed by calcium carbonate, kaolin, titanium dioxide, zinc oxide, pigments, among others. In this study a method has been developed to evaluate the fluorine content in eye shadow samples using high-resolution continuum source graphite furnace molecular absorption spectrometry and direct solid sample analysis with calibration against aqueous standard solutions. The molecular absorption was measured using only the center pixel at 606.045nm and applying gas flow in the vaporization step. The diatomic molecule CaF was generated by the addition of 100μg Ca (as Ca(NO3)2·4H2O) as the molecule-forming reagent using a pyrolysis temperature of 1000°C and a vaporization temperature of 2400°C. The characteristic mass and limit of detection were 0.68ng and 2mg kg−1, respectively. The accuracy of the method was confirmed using two certified reference materials and by comparison with solubilization of the samples using tetramethylammonium hydroxide. Seven eye shadow samples from China, Brazil and France were analyzed to confirm the applicability of the method to real samples; the concentration of fluorine was found between 0.8 and 2.7gkg−1, however there is no legislation to monitor the maximum levels of fluorine in this cosmetic.

Application of disposable starch-based platforms for sample introduction and determination of refractory elements using graphite furnace atomic absorption spectrometry and direct solid sample analysis

We propose starch-based platforms for direct solid sample introduction in GF AAS. Signal tailing for refractory elements is significantly reduced.

Signal-to-noise enhancement in TSSI–GC–IMS: Development of two dimensional sensor for detection of chemicals

Over the years, Ion Mobility Spectrometry (IMS) which refers to the techniques and cutting-edge instruments for characterizing of analytes by their gas phase mobility has been gaining popularity and validity among scientific researchers for detecting chemicals. This novel gas sensor with its high analytical speed, low detection limits, ease of use and ruggedness during transport has also become the dominant commercial technology in different industries. In spite of these paramount advantages, this detector has difficulty identifying matrix compounds. To overcome this problem a Gas Chromatograph (GC) can be used to introduce individual components of mixture into an IMS. The output signal of the hyphenated GC–IMS method is an extraordinary small, time-dependent current produced by mobile ions in atmospheric pressure. To exploit the qualitative and quantitative information hidden in this sensitive noisy signal, various signal processing methods have been nominated for spectrum filtration and improving signal-to-noise ratio (SNR). In the present paper an attempt is made to design and construct a GC–IMS instrument coupled with a Thermal Solid Sample Introduction (TSSI) module for injection of solid samples to capillary GC column. Moreover, various spectrum filtration methods for removing noise from GC–IMS signal would be investigated. The GC–IMS instrument used in this research was designed and constructed in Institute of Materials and Energy, Isfahan, Detector group and can be used as a chemical sensor for rapid detection of a broad range of chemical mixtures in many operational environments including on-board Volatile Organic Analyzer Sensor (VOAS) in space missions. The capability of constructed sensor for detection of complex mixtures has been proved by analyzing a mixture of three pesticides as test materials. Our proposed method for removing noise from the real-time TSSI–GC–IMS signal will be presented and its efficacy will be proved by offering real experiments.

Spark ablation–inductively coupled plasma optical emission for elemental depth profiling and imaging

Spark ablation was coupled to inductively coupled plasma-optical emission spectrometry (ICP-OES) for direct solid sample introduction. The preliminary applications including elemental depth profiling of metallic thin films and surface elemental imaging for solid conductive samples were explored to expand the applications of traditional ICP-OES. The parameters affecting the spark discharge for ablation sampling including electrode materials, electrode gap, discharge voltage, and gas flow rate were investigated in details. The mechanism of spark ablation was also briefly discussed with data of X-ray photoelectron spectroscopy.

Determination of fluorine in plant materials via calcium mono-fluoride using high-resolution graphite furnace molecular absorption spectrometry with direct solid sample introduction

Fluorine reacts with calcium forming gaseous CaF, which can be determined by high-resolution molecular absorption spectrometry.

Determination of Trace Chlorine in Fine Ceramics by ICP-AES Using Tungsten Boat Furnace Vaporizer and Exchangeable Sample Cuvette System as a Direct Solid Sampler

A new approach to simple solid sample digestion, subsequent vaporization, and introduction into an inductively coupled plasma was developed for the direct determination of chlorine in fine ceramic materials by atomic emission spectrometry. To each small sample cuvette made of tungsten, a powder sample was placed and weighed accurately. Following an addition of modifier solution, the cuvette was positioned on the tungsten boat furnace incorporated an electrothermal vaporizer. Then, the analyte in the sample cuvette was vaporized and introduced into the plasma; the major components of ceramic being retained. The solid ceramic samples were analyzed by using an external calibration curve prepared with the aqueous standard solutions. The detection limit of chlorine was estimated to be 0.71 ng, which corresponds to 59 ng g−1 of the chlorine concentration in solid ceramic materials. The relative standard deviation was calculated to be 3.2%. The analytical results in various ceramic materials are described.

Thermal Solid Sample Introduction–Fast Gas Chromatography–Low Flow Ion Mobility Spectrometry as a field screening detection system

The potential of Thermal Solid Sample Introduction (TSSI)–Fast Gas Chromatography (GC)–Low Flow Ion Mobility Spectrometry (LF-IMS) having been designed and constructed in Engineering Research Center of Esfahan, detector group was investigated for chemical detection capabilities. Customizing the configuration of fast GC–IMS as a high technology, provides unique solutions for rapid detection of a broad range of chemical mixtures in many operational environments. TSSI configuration provides fast and easily applied method for direct detection with no additional sample preparation or extraction. The time required for total analysis, less than 265s, was determined by the wide range of solid matrixes, including nitrate esters, nitroaromatics, and a nitramine. The fast extraction together with the short separation time limits degradation of the thermally labile compounds and decreases the peak widths, which results in larger peak intensities and a simultaneous improvement in detection limits. For signal-to-noise ratio equals to 5, the detection limits for instrument for TNT, DNT and RDX were attained 15, 10 and 50ng/μl respectively. The combination of short analysis time and low detection limits make this instrument a potential candidate for field screening techniques.

A quick analytical method using direct solid sample introduction and GC-ECD for pesticide residues analysis in crops

In this work, an analytical method for GC using direct solid sample introduction was developed to tackle the problem regarding quick detection of pesticide residue in crops and large-scale screening of samples. 10mg of the crop solid sample without sample pre-treatment was directly introduced into a modified split/splitless injector for GC analysis. A split/splitless injector was modified to quickly remove oxygen and low boiling-point matrices of the sample. The whole sampling procedure was simple and it required less than 5min. The experimental parameters including injector-port temperature, removal of oxygen and low boiling point matrices, size and the amount of the solid sample, oven temperature program were studied. Satisfactory recoveries of 6 pesticides (methyl parathion, fenitrothion, aldrin, dieldrin, endosulfan, o,p′-DDT) were obtained in maize and rice sample. Relative standard deviation was less than 15%. Experimental results showed that the proposed method was quick and reliable for pesticide residues analysis in crops.

A Review of Near‐Field Laser Ablation for High‐Resolution Nanoscale Surface Analysis

Traditional laser ablation is a well‐known method of solid sampling for surface characterization, but the resolution of the technique has been limited by the diameter of the incident laser beam and is typically on the order of 100–200 µm. Unfortunately, this microscale resolution can be too low to characterize isolated surface features that have submicron dimensions. Near‐field laser ablation is an emerging analytical tool for nanoscale, high‐resolution surface analysis. In this review, applications of near‐field laser ablation for solid sample introduction are explored. Also, a descriptive overview of the near‐field region is given, and methods of generating a near‐field region and several processes for tip manufacture are described.

Direct determination of major elements in solid plant materials by electrothermal vaporization inductively coupled plasma atomic emission spectrometry

The present work demonstrates the capability of electrothermal vaporization (ETV) to become an important tool of solid sample introduction in ICP-AES for plant sample analysis. Direct determination of Al, Ca, Fe, K, Mg, Mn, Na and Zn was investigated in powdered plant samples. Obtaining good results for major elements in plant samples was governed by some special operating conditions. The sensitivity of the method necessitated the use of ICP in radial view configuration. The behavior of elements during vaporization was studied between 500 and 2600 °C. External calibration was carried out using solid external (cellulose) spiked with aqueous standard solutions. However, performances of the analytical method were found dependent of argon flow rates. Analytical accuracy of the method was tested in three reference materials. Analytical results agreed with certified values when cellulose was used in calibration. However, K could not be determined because of excessive sensitivity. Without cellulose, it was found that Fe results were underestimated and Zn results overestimated. Relative standard deviations varied from 3 to 23%. Limits of detection varied from 1 to 80 ng g −1 from one element to the other for a typical mass sample of 2 mg.

A two-step atomizer system using a transversely heated furnace with Zeeman background correction: Design and first solid sampling applications

A two-step-atomizer consisting of a transversely heated graphite atomization tube and a movable vaporizer graphite cup is described. The atomizer is placed between the poles of an electromagnetic field providing longitudinal Zeeman-effect background correction capability. The tube and the cup are heated by independent power supplies enabling the performance of atomic absorption measurements at temporally and spatially isothermal conditions. The design of the vaporizer provides several advantageous features including direct introduction of solid and liquid samples with extremely low contamination risk and a sampling volume of up to 105 μl. The performance of this system was assessed by analysis of the bovine liver NIST SRM 1577b and of a well characterized titanium dioxide material. Calibration curves for quantification were recorded by using aqueous standards. In comparison of the results obtained by this method with the certified values and with the results of independent methods, excellent to reasonable agreement was achieved. For the elements Fe, K, Mg, Mn, Na and Zn in titanium dioxide, the achievable limits of detection were between 60 pg g − 1 (Mg) and 0.7 ng g − 1 (Fe).

On-line flow injection solid sample introduction, leaching and potentiometric determination of fluoride in phosphate rock

A flow injection method with on-line solid sample dissolution was developed for the determination of fluoride in phosphate rock. The fluoride was selectively leached (98–102.4 % recovery) from a 50-mg powdered phosphate rock sample with 0.50 M citric acid. Using the zone sampling technique the fluoride in the buffered leachate was determined by injecting 87 μL into the carrier stream using a fluoride ion-selective electrode detector. The sensing element of the electrode was housed in a home-made sleeve-type flow-through cell. On-line solid sample digestion with 0.50 M citric acid at 55 °C resulted in minimum dissolution of interfering iron and aluminum ions with improved accuracy and calibration linearity. The incorporation of relatively high level of fluoride in the carrier stream (40 μg mL −1) facilitated the determination of high levels of fluoride in phosphate rock (up to 4.1%) with out the need for excessive on-line dilution. The optimized flow system was applied for the determination of fluoride in phosphate rocks samples and a reference material at a rate of nine samples per hour with a relative standard deviation ( n = 5) of 2.95–4.0 %. Comparison of the proposed flow injection method with the standard method, which involves steam distillation from sulfuric acid solution and manual titration with thorium nitrate, showed no evidence of bias at the 95% confidence level.

Anthill Earth as a Gold Occurrence Indicator, and Gold Determination by Solid Sampling Flame Atomic Absorption Spectrometry

With the aim of avoiding cumbersome sample treatment, we present a device for the introduction of solid soil samples into AAS-flames for gold determination, as well as the proposition of earth from anthills as a gold occurrence indicator. A previous ground sample of anthill earth (0.50 mg) was weighed directly into a small recipient of polyethylene which was then connected to a sampling boronsilicate glass chamber. The sample was carried by an airflow (5 L min−1) to a quartz cell positioned between the burner top and the optical beam. The generated atomic vapor produced a transient signal which was totally integrated in three seconds. The performance was compared with conventional flame atomic absorption spectrometry after proper sample digestion. No significant differences were observed between both procedures (mean deviation ±1.90%), and a LOQ of 0.03 µg Au was achieved using the proposed method. The anthill earth was found to be very suitable for indication of gold occurrence in soils and related materials.

Cadmium determination in biological samples by direct solid sampling flame atomic absorption spectrometry

A direct solid sampling flame atomic absorption spectrometric procedure for trace determination of cadmium in biological samples has been developed. Test samples (0.05–2.00 mg) were ground and weighed into small polyethylene vials, which were connected to the device for solid sample introduction into a conventional air/acetylene flame. Test samples were carried as a dry aerosol to a quartz cell, placed between the burner and the optical path, which had a perpendicular entrance and a slit in the upper part. The atomic vapor generated in the flame produced a transient signal that was totally integrated within 1 s. The effect of operating conditions and the extent of grinding on the analytical signal were evaluated. Background signals were always low and a characteristic mass of 0.29 ng Cd was obtained. Calibration was performed using different masses of solid certified reference materials. Results obtained for certified and in-house reference materials were typically within the 95% confidence interval of the certified and/or reference value, and the precision, expressed as relative standard deviation, was between 3.8 and 6.7%. The proposed system is simple and it might be adapted to conventional atomic absorption spectrometers allowing the determination of Cd in more than 80 test samples per hour, excluding weighing.

Direct flame solid sampling for atomic absorption spectrometry: determination of copper in bovine liver

In this work a new device for the direct introduction of solid samples into flame atomizers is proposed. The determination of copper in bovine liver reference material by flame atomic absorption spectrometry (FAAS) using a conventional air–acetylene flame was chosen as an example. Between 0.05 and 0.50 mg of the test sample was weighed directly into a small polyethylene vial connected to a glass chamber. A flow of air carries the test sample as a dry aerosol to a T-shaped quartz cell positioned above the burner in the optical path. The atomic vapor generated produces a transient signal of less than 3-s duration; integrated absorbance is used for signal evaluation. Optimized conditions for air flow rate, flame stoichiometry, etc., were evaluated. There was no statistical difference between the results from the proposed system, compared with those obtained by prior sample digestion and determination by conventional FAAS. No excessive grinding of the samples was required and samples with particle size less than 80 μm were used throughout. Background signals were always low and a characteristic mass of 1.5 ng was found for Cu. The proposed system allows the determination of 60 test samples in 1 h and it can be easily adapted to conventional atomic absorption spectrometers.

On-line flow injection solid sample introduction digestion and analysis: spectrophotometric and atomic absorption determination of iron, copper and zinc in multi-vitamin tablets

An on-line flow injection system with solid sample introduction, digestion, treatment and analysis was proposed. The solid sample powder is inserted into a special chamber and carried by the digestion solution to a thermally heated PVC coil (1.4 mm i.d.). The analyte metal as the chloro-complex was retained on a coarse-particle (>0.5 mm) anion exchange resin mini column. The resin beads are held between two plastic screens which allow insoluble residue to pass through to waste. After a brief column wash, the analyte is eluted with diluted HNO 3 and determined spectrophotometrically or by atomic absorption. The proposed novel configuration of the multi-channel pinch valve allows handling slurries without tube blockage or valve damage. The system performance was tested by the determination of Fe, Zn and Cu in multi-vitamin tablets. Fe was determined spectrophotometrically as the thiocyanate complex while Zn and Cu were determined by atomic absorption. Compared with conventional digestion and analysis procedures the flow system yields a reasonably accurate relative error (RE) <2% and precise results with relative standard deviation (R.S.D.) in the range of 2.5–4.2%.

Electrospray mass spectrometry of trimethyllead and triethyllead with in‐tube solid phase microextraction sample introduction

Electrospray mass spectrometry of trimethyllead and triethyllead with in‐tube solid phase microextraction sample introduction